The poll, conducted Tuesday through Friday, shows support at 24 percent for Romney, the former governor of Massachusetts; 22 percent for Paul, a Texas congressman; and 15 percent for the surging Rick Santorum, a former U.S. senator from Pennsylvania.

But the four-day results don’t reflect just how quickly momentum is shifting in a race that has remained highly fluid for months. If the final two days of polling are considered separately, Santorum rises to second place, with 21 percent, pushing Paul to third, at 18 percent. Romney remains the same, at 24 percent.